Hi! I really liked this game!
At the end, the narrator says about having music, and if you open the 'options.rpy' file and then find these lines of code:
'## Uncomment the following line to set an audio file that will be played while
## the player is at the main menu. This file will continue playing into the
## game, until it is stopped or another file is played.
define config.main_menu_music = "example"'
Then you can uncomment (remove the hashtags) for the final line and then put the name of your music file (for example, example.mp4)
You can put the music file in your renpy games 'game' folder ^-^
Hopefully this helps, sorry if it doesn't!